Shut up brakes
Discussion
Wondering if anyone has any ideas -
- 2007 Jeep Grand Cherokee 3.0 diesel.
- front driver side wheel or brake makes an intermitent "shh...shh...shh" grinding noise when braking, frequency and volume matches road speed.
- usually worse when brakes are hot then fades away as they cool, but can occasionally happen even at walking speed when cold.
- in the past 2 years I have fitted new front hubs, new (recon) calipers, new sliders and rubbers, new pads and discs.
I got fed up with hearing it so, assuming it must be a problem with the pad or disc on that corner today I took the front brakes on both sides apart, checked and cleaned everything, ceramic brake grease on the correct areas etc and fitted another brand new set of pads and discs.... but the noise is still there, it made it before i'd gone 200 yds on the post-fit test drive, which was mildly annoying to say the least.
Calipers appear fine, pistons move ok, sliders are nice and free, and after a 20 mile drive that wheel / brake was actually cooler than the opposite side.
I am stumped, does anyone have any ideas what else i can check?
- 2007 Jeep Grand Cherokee 3.0 diesel.
- front driver side wheel or brake makes an intermitent "shh...shh...shh" grinding noise when braking, frequency and volume matches road speed.
- usually worse when brakes are hot then fades away as they cool, but can occasionally happen even at walking speed when cold.
- in the past 2 years I have fitted new front hubs, new (recon) calipers, new sliders and rubbers, new pads and discs.
I got fed up with hearing it so, assuming it must be a problem with the pad or disc on that corner today I took the front brakes on both sides apart, checked and cleaned everything, ceramic brake grease on the correct areas etc and fitted another brand new set of pads and discs.... but the noise is still there, it made it before i'd gone 200 yds on the post-fit test drive, which was mildly annoying to say the least.
Calipers appear fine, pistons move ok, sliders are nice and free, and after a 20 mile drive that wheel / brake was actually cooler than the opposite side.
I am stumped, does anyone have any ideas what else i can check?
JimSuperSix said:
after a 20 mile drive that wheel / brake was actually cooler than the opposite side.
If it's noticeably cooler, there must be something wrong with it affecting braking. The brakes on either side of any axle should be doing the same amount of work and get equally hot.I would in the following order.
Remove rotors and clean the hubs with a grinder /steel wire brush...rust build up even small can shove a disk off of true.
Hub carriers...again clean them with a grinder wire brush, any build up under the shims and rub rub rub those shims, cleanliness....is what
Check the pads you have are shaped at the edges...ie chamfered sides , cheap ones are normally square, this causes brake lining to clog up the shims, chamfered ones let the friction lining drop onto the road....
Check the caliper action...best done of the bench...you are feeling for a small sticking when the piston is pushed home..if so get the piston out and clean, the bit under the o ring is a magnet for broken down fluid and rust. As the brake retracts the o ring rolls and caused the brake to stick on ever so slightly... As a brake caliper kit is cheap...£30 ish for a set with pistons, £8 just for the o rings, no special tooling require just change them. If the caliper is not shot you only should need to with a compressor into the brake line hole for the piston to pop out. If you have to pull the things out with mole grips.....Remember hydraulic force is powerful and can overcome slight retraction faults in the pistons...its why they are pretty safe ..designed that way.
In most cases i have fixed its the pistons sticking slightly..you have to ask yourself...what is the negative force operating on the caliper to make it retract...answer not a lot, just the rubber slider boots and the centrifugal force ( i know its not real but ...) and the square cut seal causing the piston to back off a nats.. and it is only a nats.
Remove rotors and clean the hubs with a grinder /steel wire brush...rust build up even small can shove a disk off of true.
Hub carriers...again clean them with a grinder wire brush, any build up under the shims and rub rub rub those shims, cleanliness....is what
Check the pads you have are shaped at the edges...ie chamfered sides , cheap ones are normally square, this causes brake lining to clog up the shims, chamfered ones let the friction lining drop onto the road....
Check the caliper action...best done of the bench...you are feeling for a small sticking when the piston is pushed home..if so get the piston out and clean, the bit under the o ring is a magnet for broken down fluid and rust. As the brake retracts the o ring rolls and caused the brake to stick on ever so slightly... As a brake caliper kit is cheap...£30 ish for a set with pistons, £8 just for the o rings, no special tooling require just change them. If the caliper is not shot you only should need to with a compressor into the brake line hole for the piston to pop out. If you have to pull the things out with mole grips.....Remember hydraulic force is powerful and can overcome slight retraction faults in the pistons...its why they are pretty safe ..designed that way.
In most cases i have fixed its the pistons sticking slightly..you have to ask yourself...what is the negative force operating on the caliper to make it retract...answer not a lot, just the rubber slider boots and the centrifugal force ( i know its not real but ...) and the square cut seal causing the piston to back off a nats.. and it is only a nats.
Edited by martygturner on Sunday 10th April 14:40
Demelitia said:
Any witness marks on the backing plates? The sound you describe is vaguely similar to that of a backing plate catching the rusty lip on a disc as the disc rotates.
Are the mating surfaces between all the components clean and flat, especially hub to disc?
There are no backing plates so its not that, its defo a brake-pad friction rubbing sort of noise rather than grinding metal.Are the mating surfaces between all the components clean and flat, especially hub to disc?
The hub looked clean but you are right, thats the only mating surface that could affect the disc so logically that must be the cause...I will take it apart again and flap-disc or wire-wheel the hub flange just to be sure.
GreenV8S said:
JimSuperSix said:
after a 20 mile drive that wheel / brake was actually cooler than the opposite side.
If it's noticeably cooler, there must be something wrong with it affecting braking. The brakes on either side of any axle should be doing the same amount of work and get equally hot.martygturner said:
I would in the following order.
Remove rotors and clean the hubs with a grinder /steel wire brush...rust build up even small can shove a disk off of true.
Hub carriers...again clean them with a grinder wire brush, any build up under the shims and rub rub rub those shims, cleanliness....is what
Check the pads you have are shaped at the edges...ie chamfered sides , cheap ones are normally square, this causes brake lining to clog up the shims, chamfered ones let the friction lining drop onto the road....
Check the caliper action...best done of the bench...you are feeling for a small sticking when the piston is pushed home..if so get the piston out and clean, the bit under the o ring is a magnet for broken down fluid and rust. As the brake retracts the o ring rolls and caused the brake to stick on ever so slightly... As a brake caliper kit is cheap...£30 ish for a set with pistons, £8 just for the o rings, no special tooling require just change them. If the caliper is not shot you only should need to with a compressor into the brake line hole for the piston to pop out. If you have to pull the things out with mole grips.....Remember hydraulic force is powerful and can overcome slight retraction faults in the pistons...its why they are pretty safe ..designed that way.
In most cases i have fixed its the pistons sticking slightly..you have to ask yourself...what is the negative force operating on the caliper to make it retract...answer not a lot, just the rubber slider boots and the centrifugal force ( i know its not real but ...) and the square cut seal causing the piston to back off a nats.. and it is only a nats.
Thanks, as said i will start with the hub flange and give it a properly good clean.Remove rotors and clean the hubs with a grinder /steel wire brush...rust build up even small can shove a disk off of true.
Hub carriers...again clean them with a grinder wire brush, any build up under the shims and rub rub rub those shims, cleanliness....is what
Check the pads you have are shaped at the edges...ie chamfered sides , cheap ones are normally square, this causes brake lining to clog up the shims, chamfered ones let the friction lining drop onto the road....
Check the caliper action...best done of the bench...you are feeling for a small sticking when the piston is pushed home..if so get the piston out and clean, the bit under the o ring is a magnet for broken down fluid and rust. As the brake retracts the o ring rolls and caused the brake to stick on ever so slightly... As a brake caliper kit is cheap...£30 ish for a set with pistons, £8 just for the o rings, no special tooling require just change them. If the caliper is not shot you only should need to with a compressor into the brake line hole for the piston to pop out. If you have to pull the things out with mole grips.....Remember hydraulic force is powerful and can overcome slight retraction faults in the pistons...its why they are pretty safe ..designed that way.
In most cases i have fixed its the pistons sticking slightly..you have to ask yourself...what is the negative force operating on the caliper to make it retract...answer not a lot, just the rubber slider boots and the centrifugal force ( i know its not real but ...) and the square cut seal causing the piston to back off a nats.. and it is only a nats.
Edited by martygturner on Sunday 10th April 14:40
The piston actions seemed smooth but only as far as compressing them to get them over the lugs on the rear of the pads. If I have no luck with the hub flange i will look at the caliper next.
The caliper carriers were nice and clean (as were the guides) as they were all new last year, no rust on anything just a bit of dirt and they cleaned up nice and shiny.
Edited by anonymous-user on Sunday 10th April 21:04
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